Lock mechanisms are generally used to maintain the door of an enclosure in a closed condition thereby securing the enclosure from unwanted entry and the contents of the enclosure from theft. These mechanisms usually have a bolt structure carried by the door which engages a latch or recess of the door frame portion of the enclosure to maintain the door in a closed and locked position. The bolt structure is selectively moveable out of engagement with the latch recess by a pre-determined manipulation of the lock mechanism. This manipulation may be the insertion and rotation of a specially configured key, or may be the pre-determined sequence of rotations of a combination dial.
These enclosures may be safes, storage rooms, vehicles, homes, or offices. Depending on the type of enclosure, one of two common modes of bolt operation is employed. One of these modes is known as dead-bolt operation in which the bolt structure is moved between locked and unlocked positions only by manipulation of the lock mechanism. In this mode, in order to engage the bolt with the latch recess thereby locking the door of an enclosure, a positive manipulation of the lock mechanism is required.
The other common mode of bolt operation is spring-bolt operation wherein the bolt is biased to the locked position by a spring and the bolt is configured with a slanted ramp surface by which motion of the door from the open to the closed position results in automatic locking of the door. Specifically, the motion of the door causes the frame of the door or enclosure to engage the slanted surface of the bolt overcoming the bias of the spring and causing the bolt to be retracted from the locked to the unlocked position. Further motion allows the bolt to be aligned with the recess, releasing the bolt to the locked position under the urging of the spring such that the bolt automatically extends into the recess or latch of the door frame. Spring-lock operation permits locking of the door as it closes without requiring positive manipulation of the lock mechanism.
In the particular application of doors for houses, lock mechanisms have been manufactured to function by each of the described modes of bolt operation. Once a lock having one of the modes of operation was installed in a door, however, it was necessary to completely replace the lock mechanism in order to change the mode of bolt operation. Since it is very rare for two different lock mechanisms to utilize the same mounting holes or bolt locations, it is usually an expensive and destructive process to change the lock mechanism of a door in order to change the mode of bolt operation.
One common lock mechanism is the combination lock wherein the exterior surface of the door has a circular rotatable dial with numeric indicia about its periphery and a stationary marker proximate the dial as a reference point. This type of lock mechanism is operated by manipulation of the dial in a pre-determined sequence of alternating clockwise and counter-clockwise rotations aligning specified numeric indicia with the marker. The specified sequence of manipulations permits the bolt to be moved to the unlocked position by either a further manipulation of the dial or a manipulation of a separate lever or handle. A mechanism utilized to accomplish this function is exemplified by U.S. Pat. No. 4,142,388 entitled "Tumbler Wheels for Combination Locks", issued to Peter J. Phillips on Mar. 6, 1979.
Combination lock mechanisms typically include a number of rotatable tumbler wheels, each wheel having a gate member positioned at one point about its periphery for receiving and cooperating with a pawl. Each of the tumbler wheels further includes a projection on one side and an annular groove with a stop on the other side. The projection of one wheel cooperates with a groove-and-stop assembly of an adjacent tumbler wheel whereby a particular tumbler wheel may rotate a portion of a full revolution independently of the adjacent wheel and then the projection engages the stop contained within the groove causing simultaneous subsequent rotation of the adjacent tumbler wheel.
The stop, groove and projection, and the gate means have a pre-determined angular orientation which dictates one of the rotational manipulations required of the combination lock dial. The proper sequence of manipulations causes the gate means of each of the multiple tumbler wheels to become aligned such that a single pawl member may rotate radially inward with respect to the multiple tumbler wheels into the gate members. This alignment of the gate means and resulting motion of the pawl places the lock in a condiiton which permits unlocking motion of the bolt by a further manipulation of the lock mechanism.
It is also commonly known for combination locks to have a changeable combination. Once each of the gate means of the tumbler wheels has been aligned as just described, a keyway portion of each tumbler wheel is similarly aligned and may receive a specially configured key. For the combination lock to have a changeable combination, it is necessary that the tumbler wheels have a multi-part construction such that the angular orientation of the stop and projection relative to the gate means may be changed. Typical tumbler wheels are comprised of an outer gate ring, including a gate for cooperation with a pawl, an inner drive ring with a projection, stop and groove assembly, and a cam, securing or locking mechanism for causing the outer gate ring and the inner drive ring to rotate in a unitary manner.
Prior tumbler wheels had extensive multi-part locking devices for securing the gate ring to the inner drive ring preventing inadvertent rotation of the gate formed as part of the gate ring relative to the inner drive ring having the projection, groove and stop. These locking devices are expensive to manufacture, are complex to assemble, may be unreliable, and required a specially configured key and complex series of key manipulations in order to change the lock combination.